Locomotive control system



Patented Feb. 20, 1945 LOCOMOTIVE CONTROL SYSTEM Cyril E. Baston, Pittsburgh, Pa., assignor to West- I inghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsyl- Vania Application August 11, 1942, Serial No. 454,375

6 Claims.

My invention relates, generally, to control systems and, more particularly, to systems for controlling the operation of electric locomotives.

The present tendency in the design of alternating current locomotives is to increase the amount of power in a single unit. Since the cross-sectional area of the locomotive cab is fixed by the clearances of the railroad on which the locomotive is to operate, the additional space necessary for mounting the larger equipment can be obtained only by lengthening the cab. While this is satisfactory for most of the equipment, a point is reached in the design of the main transformer where increasing the capacity by increasing the length only results in an uneconomical, if not impractical design.

One solution is to provide two main transformers in place of one. In order to distribute the weight properly, the two transformers should be placed at opposite ends of the locomotive near the cab center pins. However, the provision of two main transformers introduces problems in the control scheme requiring either duplicate sets of preventive coils and duplicate tap-changing switches, or numerous heav cables from each transformer to a single set of preventive coils and switches. Either of the foregoing alternatives results in increased cost and weight.

An object of my invention is to provide a locomotive control system which does not have the foregoing disadvantages.

Another object of my invention is to decrease the number of tap-changing switches required to provide a given number of accelerating notches.

A further object of my invention is to reduce the size of the transformers required for a certain amount of power.

Other objects of my invention will be explained fully hereinafter or will be apparent to those skilled in the art.

In accordance with my invention the secondary windings of two transformers are first connected in differential-series relation. Since the secondaries are of unequal voltages, a resultant voltage is impressed across the traction motors. Tap-changing switches connected to the secondary of the smaller transformer are closed in the proper sequence togradually reduce the differential voltage, resulting in an increase in the voltage impressed on the motors. This is continued until the smaller transformer is completely out out of the motor circuit and the larger transformer is supplying all the power for the motors. The smaller transformer is then so reconnected into the circuit that its voltage is gradually formers.

added to that of the larger transformer the sequential operation of the tap-changing switches, thereby increasing the motor voltage until the maximum voltage is reached.

For a fuller understanding of the nature and objects of my invention, references may be had to the following detailed. description, taken in conjunction with the accompanying drawing, in

which:

Figure l is a diagrammatic View of a control system embodying my invention; and

Fig. 2 is a chart showing the sequence of operation of the switches illustrated in Fig. 1.

Referring to the drawing and particularly to Fig. l, the system shown therein comprises motors 2| and 22 which may be of a type suitable for propelling a locomotive (not shown), a pair of transformers 23 and 24 having primary windings 25 and 2t and secondary windings 21 and 28, respectively, and a pantograph current collector 29 which engages a trolley conductor 30. The trolley conductor 3% may be energized from any suitable source of power, such as a power generating station (not shown).

A plurality of tap-changing switches I to 12, inclusive, and preventive coils l3, l4, and I5 are connected together through buses IE, IT, I8, and 19 in the usual three-preventive coil scheme for controlling the voltage applied to the traction motors. However, in the present system the tap-changing switches are connected only to taps on the secondary winding 28 of the transformer 24 which is the smaller of the two transihe secondary winding 23 has a lower voltage than the secondary winding 2'! of the transformer 23. In order to simplify the drawing and description, only a few tap-changing switches have been shown. It will be understood that additional switches may be added, if desired.

In addition to the tap-changing switches,- switches X, Y, and Z are provided for interconnecting the secondary windings 2'! and 28. When the switches X and Z are closed, the secondary windings 21 and 28 are connected to the motors 2| and 22 in differential-series relation. When the switch Y is closed, the secondary windings are connected in cumulative-series relation. The primary windings 25 and 25 are connected in parallel-circuit relation at all times.

The operation of the tap-changing switches.

and the switches X, Y, and Z may be controlled by a drum controller (not shown) in a manner well known inthe art. There sequence of operatlon is shown in Fig. 2. r

As indicated in Fig. 2, the tap-changing switches l, 2, 3, and 4 and the disconnect switches X and Z are closed on the first notch or step of acceleration. With this connection, the voltage of the secondary winding 28 is subtracted from that of the secondary winding 21. The voltages of these two secondary windings are such that their difference is the voltage required by the motors on the first notch.

As the acceleration progresses, switch I opens and switch 5 closes, switch 2 opens and switch 6 closes and so on, thereby reducing the voltage being subtracted from the voltage of the secondary winding 21, until switches 9, H], H, and I2 are closed. At this time, the secondary'winding 28 is entirely disconnected from the circuit and the disconnect switch X is opened and the switch Y closed. The closing of the switch Y connects the secondary windings 21 and 28 in cumulative-series relation. No change in voltage occurs during this transition which is, therefore,

not diflicult. Upon the closing of the switch Y,

the switches a, it, ii, and I2 are opened, and the switch Z is opened after the switches 9, I0, I i, and I2 are opened.

The switches I, 2, 3, and 4 are again closed, thereby adding a part of the voltage of the secondary winding 28 to that of the winding 21, resulting in an increase of the voltage applied to the motor circuit. The tap-changing switches are operated in the same sequence as before until the switches 9, iii, H, and 12 are closed, thereby gradually increasing the motor voltage until the sum of the voltages of the entire secondary windings of the two transformers is applied to the motor circuit, which completes the accelerating cycle.

The present system not only provides an increase in the power capacity of the main transformers, but also reduces the number of tapchanging switches required for a certain number of notches or accelerating steps. Likewise. the number of taps that must be brought out of the transformers is reduced. Since all of the taps are on the one transformer, only two leads are required between the two transformers, instead of a lead for each tap, as required with the usual scheme of connecting the secondary windings in parallel-circuit relation. Furthermore, the disconnect switches X, Y, and Z are not required to open a circuit while carrying current; therefore, they need not be provided with are chutes and blow-out coils.

Since numerous changes may be made in the above-described construction, and different embodiments of the invention may be made without departing from the spirit and scope thereof, it is intended that all matter contained in the foregoing description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

I claim as my invention:

1. In a control system, in combination, a pair of transformers having primary windings and secondary windings, switching means for con necting all of said secondary windings in differential-series relation, tap-changing means .for

gradually reducing the differential voltage, and

additional switching means for connecting the secondary windings in cumulative-series relation,

' said additional switching means cooperating with said switchingmeans to make a closed circuit transition from differential to cumulative-series relation said tap-changing .means being operated to gradually increasethe cumulative voltage,

additional switching means for connecting the secondary windings in cumulative-series relation, said additional switching means cooperating with said switching means to make a closed circuit transition from differential to cumulative-series relation, said tap-changing means being oper- .ated to gradually increase the cumulative voltage, thereby controlling the terminal voltage of the secondary windings without changing the voltage of the primary windings.

3. In a control system, in combination, a pair of transformers having primary windings and secondary windings, switching means for conmeeting all of said secondarywindings in differential-series relation, a plurality of tap-changing switches connected to only one of said secondary windings and closed in sequential relation to reduce the differential voltage, and additional switching means for connecting the secondary windings in cumulative-series relation, said additional switching means cooperating with said switching means to make a closed circuit transition from differential to cumulative-series relation, said tap-changing switches being reclosed in sequential relation to increase the cumulative voltage, thereby controlling the terminal voltage of the secondary windings without changing the voltage of the primary windings.

4. In a control system, in combination, a pair of transformers having primary windings and secondary windings, said secondary windings being of unequal voltages, means for continuously connecting the primary windings to a power source in parallel-circuit relation, means for connecting all of the secondary windings in differential-s'eries relation, switching means connected to the said secondary winding having the lower voltage for gradually reducing the differential voltage, and means for connecting the secondary windings in cumulative-series relation, said switching means being operated to gradually increase the cumulative voltage, thereby controlling the terminal'voltage of the secondary windings without changing the voltage of the primary windings.

5. In a control system, in combination, a pair of transformers having primary windings and secondary windings, said secondary windings being of unequal voltages, means for continuously connecting the primary windings to a power source in parallel-circuit relation, switching means for connecting all of the secondary. windings in differential-series relation, tap-changing switches connected to the said secondary winding having the lower voltage for gradually reducing the differential voltage, and additional switching means for connecting the secondary windings in cumulative-series relation, said tapchanging switches being operated to gradually increase the cumulative voltage, thereby controlling the terminal voltage of the secondary windingswithout changing the voltage of the primary windings.

6. In a control system, in combination, a pair of transformers having primary windings and secondary windings, said secondary windings being of unequal voltages, means for continuously connecting the primary windings to a power source in parallel-circuit relation, switching means for connecting all of the secondary windings in differential-series relation, a plurality of tap-changing switches connected to only the said secondary winding having the lower voltage and closed in sequential relation to reduce the differential voltage, and additional switching means for connecting the secondary windings in cumulative-series relation, said tap-changing switches 

